What is Differential Protection?

What is Differential Protection?

Differential Protection Definition

Differential protection is a method used to clear internal faults in the stator winding of a generator or alternator.

Current Transformers

Two sets of current transformers (CTs) are used, one on the line side and one on the neutral side, and their characteristics must match to avoid relay malfunctions.

Stabilizing Resistor

A stabilizing resistor in series with the relay prevents operation due to external faults or CT saturation.

Percentage Biasing

Percentage biasing in differential relays helps manage spill current from mismatched CTs, preventing unwanted relay operation.

Relay Operation

The differential relay operates during internal faults when the operating coil’s torque overcomes the restraint coil’s torque, ensuring reliable protection.